Remove the coercion from
&mut T from the language.
Currently, the coercion between
&mut T can be a hazard because it can lead to surprising mutation where it was not expected.
The coercion between
&mut T should be removed.
Note that methods that take
&mut self can still be called on values of type
Box<T> without any special referencing or dereferencing. That is because the semantics of auto-deref and auto-ref conspire to make it work: the types unify after one autoderef followed by one autoref.
&mut T may be convenient.
An alternative is to remove
&T coercions as well, but this was decided against as they are convenient.
The impact of not doing this is that the coercion will remain.